Embed a Sidecar

Declare at build time

tynd.config.ts


export default {
  runtime: "lite",
  backend: "backend/main.ts",
  frontendDir: "dist",
  sidecars: [
    { name: "ffmpeg", path: "bin/ffmpeg" },
  ],
} satisfies TyndConfig;

name — what your code asks for at runtime.
path — where the file lives at build time, relative to project root.

Use at runtime


import { sidecar, process } from "@tynd/core/client";
 
export async function transcode(input: string, output: string) {
  const ffmpeg = await sidecar.path("ffmpeg");
  const { stdout, stderr, code } = await process.exec(ffmpeg, {
    args: ["-i", input, "-c:v", "libx264", "-y", output],
  });
  if (code !== 0) throw new Error(stderr);
  return output;
}

sidecar.path() returns the extracted on-disk path (chmod +755 on Unix, ready to execute).

Platform-specific binaries

Tynd doesn’t cross-compile. For CI matrix builds, stage the right binary per host before tynd build:


- name: Stage ffmpeg
  shell: bash
  run: |
    case "${{ matrix.target }}" in
      windows-x64) curl -L -o bin/ffmpeg.exe https://…/ffmpeg-win.exe ;;
      linux-x64)   curl -L -o bin/ffmpeg https://…/ffmpeg-linux ;;
      macos-arm64) curl -L -o bin/ffmpeg https://…/ffmpeg-macos-arm64 ;;
    esac
    chmod +x bin/ffmpeg*
 
- run: bunx tynd build --bundle

Long-running sidecar (streaming output)


import { terminal, sidecar } from "@tynd/core/client";
 
const ffmpeg = await sidecar.path("ffmpeg");
const t = await terminal.spawn({
  shell: ffmpeg,
  args: ["-i", input, "-progress", "pipe:1", "-c:v", "libx264", output],
});
 
t.onData((bytes) => {
  const text = new TextDecoder().decode(bytes);
  const m = text.match(/out_time_ms=(\d+)/);
  if (m) reportProgress(parseInt(m[1]) / 1_000_000);
});
 
t.onExit((code) => {
  if (code !== 0 && code !== null) alert("ffmpeg failed");
});

Size tradeoff

Sidecars don’t get zstd-compressed — they inflate your binary by their raw size. A 60 MB ffmpeg-static ships in your installer. Alternatives:

Download on first launch — ship a lean binary, http.download the sidecar to os.dataDir() the first time the user needs it.
Use the system binary if available — process.exec("ffmpeg", …) first; fall back to bundled.

Related: sidecar API · Sidecars guide.